Active Soil Nail Wall Underpinning Solution for the Bruce Museum Project-Video

Video Transcription

Video Summary

Jonathan Ernst presented the geotechnical solution for the Bruce Museum’s $60 million expansion in Greenwich, Connecticut. The three-story addition required deep excavation beside a historic building, with existing footings as close as six inches to the proposed work and bedrock sloping from about four to over 16 feet below grade. Traditional underpinning posed safety, movement, and schedule challenges.<br /><br />The team instead designed a permanent, post-tensioned soil nail wall to support excavation and protect the existing structure. The flexible system accommodated changing cut heights, nearby footing and slab surcharges, and areas where excavation reached bedrock. Construction was carefully sequenced, with full-time monitoring and field coordination. Nails were tensioned to about half their design load, and the contractor carried out additional shotcrete strength testing.<br /><br />Automated monitoring recorded building movement every two hours for roughly four months. Results showed very little movement, within project tolerances. The solution provided safe, adaptable support while avoiding the risks and constraints of conventional underpinning.

Keywords

geotechnical solution

soil nail wall

deep excavation

post-tensioned support

building monitoring